fix(config): add serde(default) to TeeConfig fields

[fkztw]

Summary

• TeeConfig fields lack #[serde(default)], causing the entire Config deserialization to fail when users specify a [tee] section in config.toml but omit some fields (e.g. max_file_size)
• Since call sites use Config::load().map(...).unwrap_or_default() to silently handle errors, all user settings (including hooks.exclude_commands) are silently ignored with no warning
• Add #[serde(default = "...")] to every TeeConfig field so partial [tee] sections deserialize correctly
• Add tests for partial and empty deserialization

Reproduction

# ~/.config/rtk/config.toml (Linux) or ~/Library/Application Support/rtk/config.toml (macOS)
[hooks]
exclude_commands = ["curl", "helm"]

[tee]
enabled = true
mode = "failures"
max_files = 20
# max_file_size is omitted — this causes the ENTIRE config to fail silently

$ rtk config
Config: ~/Library/Application Support/rtk/config.toml

Error: TOML parse error at line 35, column 1
   |
35 | [tee]
   | ^^^^^
missing field `max_file_size`

When rtk config is not called directly, Config::load() fails silently and falls back to defaults — all user settings are ignored without any warning.

Test plan

• cargo fmt --all --check — passed
• cargo clippy --all-targets — no new warnings
• cargo test --all — 1116 passed, 3 ignored
• New test_tee_config_partial_deserialize — verifies omitting max_file_size does not fail
• New test_tee_config_empty_deserialize — verifies a completely empty [tee] section uses defaults

🤖 Generated with Claude Code

[CLAassistant]

All committers have signed the CLA.

[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

[fkztw]

Rebased on develop as requested. Git automatically detected the file rename from src/tee.rs → src/core/tee.rs (from PR #826), so no manual path updates were needed.

Verification:

• cargo fmt --all --check — passed
• cargo clippy --all-targets — no new warnings
• cargo test --all — 1130 passed, 3 ignored (up from 1116 before rebase, reflecting tests added in develop)

The fix and tests remain functionally identical — only the file location changed.

[rtk-release-bot]

This pull request has been automatically marked as stale due to 90 days of inactivity. If this pull request is still relevant, please leave any comment (for example, "bump"), and we'll keep it open. Your contribution is very much appreciated — we're sorry we haven't been able to review it yet.

[KuSh]

Thanks for digging into this one. The [tee] section was reworked by #3278, merged 2026-09-09, which moved recovery settings to [retriever] and kept [tee] as a legacy section parsed into a struct where every field is optional and the struct carries serde(default), so a partial [tee] block no longer fails the whole config load. The regression case you added is covered on develop by test_legacy_tee_disabled_maps_to_disabled_mode and test_legacy_tee_never_mode_maps_to_disabled_mode, both of which parse a [tee] section with a single field. Closing as already fixed, but please comment or reopen if you find a config shape that still parses badly.